Kaloxylon Hookeri and Lyginodendron Oldhamium. 1 1 1 



Williamson expresses himself somewhat doubtfully, but 

 concludes with the remark that it is difficult to believe that 

 they have been other than roots. 



Such is a brief description of the anatomical structure 

 of the different forms of Kaloxylon Hookeri, Will., as given 

 by Williamson. It is not proposed to revise that description 

 on this occasion, but rather to discuss the morphological 

 nature of the fossils to which it applies. 



Taking the last series of specimens first, I think there 

 can be no doubt that, as Williamson found it difficult to 

 doubt, they are really roots. This conclusion has been 

 reached after a careful comparison of Williamson's descrip- 

 tion and figures with a large number of specimens in my 

 own cabinet and in the cabinets of friends. The struc- 

 tures that have given origin to the fossils were so delicate, 

 however, that they are rarely preserved in a perfect condi- 

 tion, and have, besides, generally suffered more or less from 

 compression. Still, where the central cylinder is fairly com- 

 plete, it is unmistakeably triarch, tetrarch, or pentarch, &c, 

 and both the structure and the appearance points to a centri- 

 petal development of the xylem strands. In a few cases, 

 what appears to be a pericycle and endodermis may be seen 

 between the outer edges of the xylem plates and the cortex. 



The two peripheral layers of cells which Williamson 

 seems to combine as an epidermal layer, should, I think, be 

 interpreted differently. The outermost is not characterised 

 in the way we should expect in a true epidermis, and rather 

 resembles the piliferous layer of roots, while the subjacent 

 layer is not unlike the suberous layer of the same organs. 



Passing on to the specimens of which the type is 

 figured by Williamson in the XHIth Memoir* the root- 

 like appearance is unmistakeable, and the structure har- 

 monises better with that of a root than that of a stem.f 

 The variation of the shape of the central cylinder or stele, 



•Phil. Trans., 1887. PI. 24, Fig. 27. t PL II., Fig. 2. 



